But Mariners general manager Jerry Dipoto said Wednesday that Hernandez escaped serious injury and is expected to miss only one spring start.
Talking on the Wheelhouse Podcast, Dipoto said, "It was one of those moments that stops your heart a little bit. But once we got some feedback from the training staff and doctors and ultimately took three sets of images to make sure he's in a good place, I was very encouraged when he walked in yesterday with minimal swelling, the pain was down, and there were no obvious signs of a fracture or break."
Mariners manager Scott Servais said Thursday that Hernandez still has some swelling in his arm and the team hopes the injury is just a minor setback.
"He's anxious, but you do have to let it run its course a little bit," Servais said.
Hernandez made 16 starts last season, pitching only 86⅔ innings, his fewest since his rookie season in 2005. He had two stints on the disabled list, with right shoulder inflammation and right shoulder bursitis.
"Felix is critically important to us," Dipoto said. "I think he looks great. His breaking balls, the spin particularly with his curveball, has been in midseason form since his second bullpen. I'm very encouraged by the way he's commanding his pitches. Frankly, I thought the first inning he threw in Mesa, if Felix Hernandez shows up and does that, we're going to be very happy with the outcome."
Hernandez, 31, had been scheduled to start again Saturday night against the Angels in Peoria, Arizona, but that will be pushed back. Servais said the initial plan was for Hernandez to throw around 25 innings this spring training, but that number is now expected to be lower
The Associated Press contributed to this report.